pub fn is_subsequence(s: String, t: String) -> bool {
    let s = s.as_bytes();
    let t = t.as_bytes();
    let s_len = s.len();
    let t_len = t.len();
    let mut i = 0;
    let mut j = 0;
    while i < s_len && j < t_len {
        if s[i] == t[j] {
            i += 1;
        }
        j += 1;
    }
    return i == s_len;
}
